1. Field
This disclosure relates generally to semiconductors, and more specifically, to the calibration of integrated circuits to compensate for offset errors.
2. Related Art
Integrated circuits typically incorporate sensing devices. Examples of such sensing devices include temperature sensors and motion sensors such as accelerometers. Clearly the accuracy of such sensors is of paramount importance. There are numerous potential sources of errors which can cause a sensor to be inaccurate. Examples of fixed errors include errors in the conversion of a sensed signal to a voltage, an analog to digital (A/D) conversion of a signal, component resistances and display resolutions, just to highlight a few. Another error source is generally described as an offset error. Sources of offset error are due to device to device offset variation (trim errors and lack of resolution), mechanical stresses, for example mounting stress, temperature stress and moisture stress, and electrical changes, such as EMI or moisture changes for example. Initial offset error may be compensated by a factory calibration by the manufacturer of an integrated circuit containing a sensor. Also, an automatic zeroing of the offset errors is needed by an end-user of the integrated circuit after the integrated circuit is placed on a circuit board in a system. When an integrated circuit sensor is placed in a system the electrical environment is modified for the integrated circuit and the sensor will likely no longer be ideally calibrated. Others have permitted an integrated circuit to use a command, known as an auto-zero command, to perform a user calibration of the sensor. However, auto-zero commands require a special command function to be created for the integrated circuit and instructing an end user of what the command mechanism is, whether the mechanism occurs by user input or automatically. Automatic auto-zero mechanisms must detect the presence of one or more system conditions for auto-zeroing to occur. There can be uncertainty as to when those conditions are met and therefore to verify that a calibration was made. A need exists for a simpler mechanism to permit a user to accurately calibrate sensor products in the field.